Escape sequences

Escape sequences are used to represent certain special characters within string literals and character constants.

The following escape sequences are available. ISO C requires a diagnostic if the backslash is followed by any character not listed here:

Escape sequence	Description	Representation
Simple escape sequences
`\'`	single quote	byte `0x27` in ASCII encoding
`\"`	double quote	byte `0x22` in ASCII encoding
`\?`	question mark	byte `0x3f` in ASCII encoding
`\\`	backslash	byte `0x5c` in ASCII encoding
`\a`	audible bell	byte `0x07` in ASCII encoding
`\b`	backspace	byte `0x08` in ASCII encoding
`\f`	form feed - new page	byte `0x0c` in ASCII encoding
`\n`	line feed - new line	byte `0x0a` in ASCII encoding
`\r`	carriage return	byte `0x0d` in ASCII encoding
`\t`	horizontal tab	byte `0x09` in ASCII encoding
`\v`	vertical tab	byte `0x0b` in ASCII encoding
Numeric escape sequences
`\nnn`	arbitrary octal value	code unit `nnn`
`\xn...`	arbitrary hexadecimal value	code unit `n...` (arbitrary number of hexadecimal digits)
Universal character names
`\unnnn` (since C99)	Unicode value in allowed range; may result in several code units	code point `U+nnnn`
`\Unnnnnnnn` (since C99)	Unicode value in allowed range; may result in several code units	code point `U+nnnnnnnn`

Range of universal character names

If a universal character name corresponds to a code point that is not 0x24 ('$'), 0x40 ('@'), nor 0x60 ('`') and less than 0xA0, or a surrogate code point (the range 0xD800-0xDFFF, inclusive), or greater than 0x10FFFF, i.e. not a Unicode code point(since C23), the program is ill-formed. In other words, members of basic source character set and control characters (in ranges 0x0-0x1F and 0x7F-0x9F) cannot be expressed in universal character names.

(since C99)

Notes

\0 is the most commonly used octal escape sequence, because it represents the terminating null character in null-terminated strings.

The new-line character \n has special meaning when used in text mode I/O: it is converted to the OS-specific newline byte or byte sequence.

Octal escape sequences have a length limit of three octal digits but terminate at the first character that is not a valid octal digit if encountered sooner.

Hexadecimal escape sequences have no length limit and terminate at the first character that is not a valid hexadecimal digit. If the value represented by a single hexadecimal escape sequence does not fit the range of values represented by the character type used in this string literal or character constant (char, char8_t(since C23), char16_t, char32_t(since C11), or wchar_t), the result is unspecified.

A universal character name in a narrow string literal or a 16-bit string literal(since C11) may map to more than one code unit, e.g. \U0001f34c is 4 char code units in UTF-8 (\xF0\x9F\x8D\x8C) and 2 char16_t code units in UTF-16 (\xD83C\xDF4C)(since C11).

(since C99)

A universal character name corresponding to a code pointer greater than 0x10FFFF (which is undefined in ISO/ISC 10646) can be used in character constants and string literals. Such usage is not allowed in C++20.

(since C99)
(until C23)

The question mark escape sequence \? is used to prevent trigraphs from being interpreted inside string literals: a string such as "??/" is compiled as "\", but if the second question mark is escaped, as in "?\?/", it becomes "??/"

(until C23)

Example

#include <stdio.h>
 
int main(void)
{
    printf("This\nis\na\ntest\n\nShe said, \"How are you?\"\n");
}

Output:

This
is
a
test
 
She said, "How are you?"

References

C17 standard (ISO/IEC 9899:2018):

5.2.2 Character display semantics (p: 18-19)
6.4.3 Universal Character names (p: 44)
6.4.4.4 Character constants (p: 48-50)

C11 standard (ISO/IEC 9899:2011):

5.2.2 Character display semantics (p: 24-25)
6.4.3 Universal Character names (p: 61)
6.4.4.4 Character constants (p: 67-70)

C99 standard (ISO/IEC 9899:1999):

5.2.2 Character display semantics (p: 19-20)
6.4.3 Universal Character names (p: 53)
6.4.4.4 Character constants (p: 59-61)

C89/C90 standard (ISO/IEC 9899:1990):

2.2.2 Character display semantics
3.1.3.4 Character constants

Docs

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Escape sequences

Range of universal character names

Notes

Example

References

See also